Yellow: Make UART5 the default UART in U-Boot (#1847)

buildroot-external/board/raspberrypi/yellow/patches/uboot/0001-drivers-bcm283x-don-t-explicitly-disable-init.patch

@@ -0,0 +1,54 @@
+From 78704bc154d695ee16fdf8396f4d60b740190014 Mon Sep 17 00:00:00 2001
+Message-Id: <78704bc154d695ee16fdf8396f4d60b740190014.1649951002.git.stefan@agner.ch>
+From: Stefan Agner <stefan@agner.ch>
+Date: Thu, 14 Apr 2022 12:15:26 +0200
+Subject: [PATCH 1/2] drivers: bcm283x: don't explicitly disable init
+
+It seems that the reason why init doesn't succeed is the lack of clock
+support in U-Boot. Setting the default clock of 48MHz for the PL011
+UARTs makes reinitialization work consistently.
+
+Note that for the first UART the "skip-init" is anyways set in the
+device tree. This will only affect probing of UARTs not enabled by
+firmware.
+
+Signed-off-by: Stefan Agner <stefan@agner.ch>
+---
+ drivers/serial/serial_bcm283x_pl011.c | 6 ------
+ include/configs/rpi.h                 | 3 +++
+ 2 files changed, 3 insertions(+), 6 deletions(-)
+
+diff --git a/drivers/serial/serial_bcm283x_pl011.c b/drivers/serial/serial_bcm283x_pl011.c
+index 2d2e970316..182274036c 100644
+--- a/drivers/serial/serial_bcm283x_pl011.c
++++ b/drivers/serial/serial_bcm283x_pl011.c
+@@ -51,12 +51,6 @@ static int bcm283x_pl011_serial_probe(struct udevice *dev)
+ 	if (ret)
+ 		return ret;
+ 
+-	/*
+-	 * TODO: Reinitialization doesn't always work for now, just skip
+-	 *       init always - we know we're already initialized
+-	 */
+-	plat->skip_init = true;
+-
+ 	return pl01x_serial_probe(dev);
+ }
+ 
+diff --git a/include/configs/rpi.h b/include/configs/rpi.h
+index e24c94c7d2..98ba4dc052 100644
+--- a/include/configs/rpi.h
++++ b/include/configs/rpi.h
+@@ -40,6 +40,9 @@
+ #define CONFIG_SYS_BOOTM_LEN		SZ_64M
+ #endif
+ 
++/* Define PL011 default clock */
++#define CONFIG_PL011_CLOCK		48000000
++
+ /* Devices */
+ /* GPIO */
+ #define CONFIG_BCM2835_GPIO
+-- 
+2.35.1
+

buildroot-external/board/raspberrypi/yellow/patches/uboot/0002-drivers-bcm283x-allow-to-spawn-any-PL011-UART.patch

@@ -0,0 +1,68 @@
+From c2447aa922068cebd9bbaac45acae3d853abf687 Mon Sep 17 00:00:00 2001
+Message-Id: <c2447aa922068cebd9bbaac45acae3d853abf687.1649951002.git.stefan@agner.ch>
+In-Reply-To: <78704bc154d695ee16fdf8396f4d60b740190014.1649951002.git.stefan@agner.ch>
+References: <78704bc154d695ee16fdf8396f4d60b740190014.1649951002.git.stefan@agner.ch>
+From: Stefan Agner <stefan@agner.ch>
+Date: Thu, 14 Apr 2022 12:18:41 +0200
+Subject: [PATCH 2/2] drivers: bcm283x: allow to spawn any PL011 UART
+
+The current code checks pinmux for the first PL011 only. Raspberry Pi 4
+has multiple PL011 UARTs. This code prevents probing of other UARTs in
+case the first PL011 UART is not active.
+
+Furthermore, U-Boot supports pinmuxing, hence the pins should be muxed
+at this point anyway. Drop the check entirly.
+
+This allows to use other UARTs as stdout paths (e.g. stdout-path =
+"serial5:115200n8").
+
+Signed-off-by: Stefan Agner <stefan@agner.ch>
+---
+ drivers/serial/serial_bcm283x_pl011.c | 27 ---------------------------
+ 1 file changed, 27 deletions(-)
+
+diff --git a/drivers/serial/serial_bcm283x_pl011.c b/drivers/serial/serial_bcm283x_pl011.c
+index 182274036c..98628e1ca4 100644
+--- a/drivers/serial/serial_bcm283x_pl011.c
++++ b/drivers/serial/serial_bcm283x_pl011.c
+@@ -11,37 +11,10 @@
+ #include <serial.h>
+ #include "serial_pl01x_internal.h"
+ 
+-/*
+- * Check if this serial device is muxed
+- *
+- * The serial device will only work properly if it has been muxed to the serial
+- * pins by firmware. Check whether that happened here.
+- *
+- * @return true if serial device is muxed, false if not
+- */
+-static bool bcm283x_is_serial_muxed(void)
+-{
+-	int serial_gpio = 15;
+-	struct udevice *dev;
+-
+-	if (uclass_first_device(UCLASS_PINCTRL, &dev) || !dev)
+-		return false;
+-
+-	if (pinctrl_get_gpio_mux(dev, 0, serial_gpio) != BCM2835_GPIO_ALT0)
+-		return false;
+-
+-	return true;
+-}
+-
+ static int bcm283x_pl011_serial_probe(struct udevice *dev)
+ {
+-	struct pl01x_serial_plat *plat = dev_get_plat(dev);
+ 	int ret;
+ 
+-	/* Don't spawn the device if it's not muxed */
+-	if (!bcm283x_is_serial_muxed())
+-		return -ENODEV;
+-
+ 	/*
+ 	 * Read the ofdata here rather than in an of_to_plat() method
+ 	 * since we need the soc simple-bus to be probed so that the 'ranges'
+-- 
+2.35.1
+